1. Field of Invention
The present invention relates to a photodetector and more particularly to a photodetector capable of making a measurement with a higher accuracy, a photodetecting method, a program, and a storage medium.
2. Description of the Related Art
In case of using an image display unit such as a projector, it is important that an image intended by a producer can be reproduced even if the application environment changes. As a way of thinking for adjusting the appearance of such an image, there is a way of thinking called color management in which input/output characteristcs of a device are managed to reproduce colors. Thus, for effecting an appropriate color reproduction, it is necessary to take into account a change of the application environment (e.g., a change in brightness and color of an external illumination) detected with use of a photosensor.
In case of providing a photosensor in a projector to obtain information of the application environment, an increase in cost of the entire projector is to be avoided and therefore it is impossible to use a so expensive photosensor. As the photosensor there is used, for example, a three-channel photosensor comprising a photodiode and RGB filters superimposed thereon. In this case, it is necessary to convert RGB outputs from the photosensor into tri-stimulus values XYZ. According to a method so far adopted generally, RGB outputs from a projector are measured using the foregoing photosensor and a highly accurate luminance meter, then a 3×3 matrix for conversion is obtained from the resulting correlation, and there is performed conversion from RGB to XYZ using the said matrix.
According to the above method, however, a spectral distribution of illumination is different from that of the projector, although with respect to the projector output there can be made conversion from RGB to XYZ with a high accuracy. As to illumination, therefore, it is difficult to effect a highly accurate conversion from RGB to XYZ even with use of the same matrix as the foregoing matrix.